J.J. Lynch

How Goats Learn to Distinguish Between Novel Foods That Differ in Postingestive Consequences

To better understand some of the mechanisms that control selection of novel foods differing in postingestive consequences, we offered goats current seasons (CSG) and older (OG) growth twigs from the shrub blackbrush (Coleogyne ramosissima). CSG is higher than OG in nitrogen (1.04% v. 0.74%) and it is more digestible in vitro in goat rumen fluid (48% v. 38%). Nevertheless, goats acquire a preference for OG because CSG contains much higher levels of a condensed tannin that causes a learned food aversion. When CSG and OG were offered to goat naive to blackbrush, the goats did not choose either OG or CSG exclusively, but when they finally (1) ate more CSG than OG within a meal (averages of 44 g and 16 g, respectively) and (2) ate enough CSG within the meal to acquire an aversion (average of 44 g), they ingested less CSG than OG from then onward. Accordingly, the change in food selection resulting from postingestive feedback was influenced by the amount of each food ingested within a meal. This was further shown when we varied the amounts of CSG and OG that goats ingested within a meal, and then gave them by gavage the toxin lithium chloride (LiCl). They subsequently ate less of the food eaten in the greatest amount, regardless of whether it was CSG or OG. The salience of the flavor (i.e., taste and odor) of CSG and OG also played a role in the acquired aversion to CSG. Salience evidently was due to a flavor common to both OG and CSG that was more concentrated in CSG. We conclude that the relative amounts of different foods ingested within a meal, and the salience of the flavors of those foods, are both important variables that cause goats to distinguish between novel foods that differ in postingestive consequences.

Changes in Maternal-Young Associations with Increasing Age of Lambs

Abstract A group of Merino ewes and their lambs was observed while grazing when the lambs were from 1 to 10 weeks old. Distances between lambs and their mothers or other nearest adults were recorded. Weekly recognition tests were also conducted to determine the time taken and patterns of movement of ewes to tethered lambs and lambs to tethered ewes. Mothers and their lambs were closely associated with one another for 75% of the time in the field, but variation existed between pairs. Mean distance between mother and lamb increased with lamb age, but mother and lamb when they were nearest neighbours were rarely more than 1 m apart. It was not until lambs were 6 weeks old that 80% could find their tethered mothers at 30 m. Post-weaning, 90% of lambs moved to their mothers even after a 2-month separation. When lambs were tethered, ewes moved to their lambs at 10 and 30 m for the initial 2–3 weeks, but after 4 weeks mothers rarely reached their lambs at either 10 or 30 m. These changes in behaviour pattern are discussed in relationship to the understanding and interpretation of ewe-lamb associations.

The Relative Importance of Mother and Toxicosis in the Selection of Foods by Lambs

A lambs mother and postingestive feedback both influence learning about foods, but their relative importance is unknown. We conducted a study to compare the ingestion of elm (1) by lambs whose mothers avoided elm because ingestion of elm by mother was previously paired with the toxin lithium chloride (LiCl) (M), (2) by lambs who received a mild dose of LiCl after they ingested elm, and whose mothers also avoided elm (M + L), and (3) by lambs who received LiCl after they ingested elm, but whose mothers ate elm avidly (M vs. L); in treatment (4) neither mothers nor lambs were given LiCl (C). In all four treatments, mothers and lambs ate poplar. Each lamb was exposed with its mother for 5 min/day to poplar on days 1,2, 5, 7, 9, and 11 and to elm on days 3, 4, 6, 8, 10, and 12. Following exposures to elm on days 8, 10, and 12, lambs in treatments M + L and M vs. L were given a low dose of LiCl (100 mg/kg body weight orally in a capsule) when they ingested elm to produce an aversion to elm. During the first test after weaning, lambs could choose between elm and poplar. Lambs in C took more bites of elm than did lambs in M, M + L, and M vs. L (13, 2, 2, < 1;P >F=0.003), and they also took a higher percentage of bites from elm (42, 11, 6, 1;P >F < 0.001). The number of bites of poplar did not differ among treatments (M=31, M + L=26, M vs. L=42, C=27;P >F =0.458). During the second test, when lambs were offered only elm, lambs in C took significantly more bites of elm than those in the other treatments, and lambs in M took more bites of elm than lambs in M + L, but not M vs. L (C=38, M=16, M + L=3, M vs. L=6;P >F < 0.001). During the third test, when lambs again could choose between elm and poplar, lambs in C again took more bites of elm (C=14, M=3, M + L=< 1, M vs. L=< 1;P >F=0.034), and they also took a higher percentage of bites from elm (C=26, M=5, M + L=2, M vs. L=2;P >F < 0.001), than did lambs in the other three treatments. The number of bites of poplar did not differ among treatments (M=47, M + L=43, M vs. L=62, C =41;P >F=0.223). We conclude that the response by lambs to the toxin LiCl was more important than was the mother as a social model because lambs that received LiCl avoided elm whether or not the mother ate it.

Effects of a Flavor and Food Restriction on the Response of Sheep to Novel Foods

Abstract Two methods were used to encourage sheep to eat unfamiliar foods quickly. The first method entailed restricting the amount of food offered. Lambs were fed either 750 g day−1 alfalfa pellets (slightly in excess of maintenance and 34% of ad libitum), or 1500 g day−1 (sufficient for 250 g day−1 growth and 68% of ad libitum) for 10 days and then offered a novel food (split peas). Food restriction did not increase the rate of acceptance of peas. The second method involved increasing familiarity with a flavor (onion) added to novel foods. Lambs drank water, water with 1% onion powder, water with 7% glucose, or water with 1% onion powder and 7% glucose. By day 2, intake did not differ among groups, so lambs were offered a novel food (rice) with 1% onion from days 3 to 7. There was no increase in speed of acceptance of rice with onion by lambs that drank onion-flavored solutions. Nor was there an increase in acceptance of rye (novel grain) with 1% onion when it was offered on days 8 to 11. However, on days 12–15, lambs ate more lentils (a novel food) with than without onion, and they ate corn (a familiar food) readily with or without onion. Conversely, intake dropped sharply when lambs were given a familiar food (rice) with a novel flavor (onion). Thus, lambs were reluctant to eat foods with unfamiliar flavors, whether they were added or occurred in novel foods. Food neophobia is likely to be one facet of the general phenomenon of fear exhibited in new situations, which ensures ruminants do not over-ingest toxic or nutrient-rich foods.

Food aversion conditioned in anesthetized sheep

We discovered that a food aversion could be conditioned in anesthetized sheep. Sheep were allowed to eat a familiar food (alfalfa-grain pellets) for 30 min, and 90 min later they were given either an intraruminal (IR) injection of water (C), an IR injection of LiCl (L), anesthesia followed by an IR injection of water (A), or anesthesia followed by an IR injection of LiCl (A+L). Induction of anesthesia was by an intravenous injection of pentobarbitone sodium, and maintenance of deep anesthesia was by halothane. Sheep were maintained in deep anesthesia for 2 h to ensure that the effects of LiCl on the acquisition of a food aversion, which occur within about 1 h, were completed before they awakened. When tested 5 days later, sheep that received LiCl (treatments L and A+L) consumed less alfalfa-grain pellets than sheep that did not receive LiCl (treatments C and A) (241 g vs. 306 g; p = 0.057). Intake of sheep that were anesthetized (treatments A and A+L) did not differ from that of sheep that were not anesthetized (treatments C and L) (295 g vs. 252 g; p = 0.183). Nor was there an interaction between LiCl and anesthesia (p = 0.423). Thus, we conclude that changes in preferences for foods caused by postingestive feedback occur automatically every time food is ingested (i.e., they are noncognitive), and the kind and amount of feedback is a function of the match between the foods chemical characteristics and its ability to meet the animals current demands for nutrients.

Long-term associations between Merino ewes and their offspring

Abstract The association between 10 Merino ewes and their offspring, born in 2 consecutive years, was examined over a 2.5-year period. Recognition tests were conducted and indicated a rapid decline in ewe-motivated association commencing 3–6 weeks after parturition. Field observations examined the spatial relationships between ewes and their offspring and between the two descendants of the mother. Evidence is presented to suggest the maintenance of long-term (> 2.5 years) associations between lambs and their mothers. This association appears to be caused entirely by the offsprings attraction to its mother.

The learning behaviour of sheep when introduced to wheat. II. Social transmission of wheat feeding and the role of the senses

Abstract The speed with which Merino weaners learnt to eat a novel food (wheat) in the presence of experienced wheat eaters, and the effects of various temporary sensory impairements on speed of learning, were studied. In Experiment 1, sheep were individually introduced to wheat in the presence of 1 or 4 experienced wheat eaters for 15 min in each of 5 consecutive days. Twelve of 16 inexperienced sheep ate wheat on the second day of exposure and 15 16 were feeding by Day 5. The mean intake of these groups was greater than 30 g/head/day. The control group, which was offered wheat in the absence of experienced wheat eaters, failed to consume any wheat over 5 days. Social transmission of wheat eating from the experienced to the naive sheep had clearly occurred very rapidly. In Experiment 2, sheep with olfaction, vision or hearing, or combinations of these senses, temporarily impaired were similarly introduced to wheat in the presence of wheat eaters. Rapid wheat acceptance occurred in all except sheep with impairment of olfaction, vision and hearing. This indicates very efficient substitution of one sense for another in learning to eat wheat. All three senses may be used in learning associated with the social transmission of feeding behaviour, but it has not proved possible to determine a major role for any one sense.

The learning behaviour of sheep when introduced to wheat. I. Wheat acceptance by sheep and the effect of trough familiarity

Abstract Merino weaners with no prior experience of eating wheat or of feeding in troughs were used to study their behavioural responses to novel situations and to the speed with which they learnt to eat wheat. Two groups of 8 sheep grazing on pasture were individually penned and fed in troughs for 15 min/day for 20 days. Group 1 was given wheat every day, whilst Group 2 received hay for the first 12 days and then wheat for the next 8 days. It took 14 days for all sheep in Group 1 to begin eating wheat, but 6 of Group 2 ate wheat 2 days after it was first offered. The results suggest there may be 3 phases in sheep learning to eat wheat. It seems that sheep must overcome fear of the trough and of the wheat. Finally, they must learn to prehend, chew and swallow wheat.

Social organization of Merino sheep of different ages, sex and family structure.

Abstract Four different groups of Merino sheep were established and social interactions were examined in paddocks which were barren or with trees and other topographic features. Two groups had been established for 2 years. One group consisted of ewes of the same age and the other contained mothers and their unweaned offspring aged 2 and 1 year. Two other groups were established recently: one consisted of sheep of different sexes whose ages ranged from 1 to 5 years and the other group contained ewes of two different age groups. Age effects on cohesive and aggressive behaviours were apparent, with older animals being involved in more fights (usually between themselves), initiating more movements and showing more attention behaviours. In dominance tests the number of fights was significantly higher in the single sex, single age group. In the field, the family group was markedly less responsive in terms of fighting, movement and attention behaviours when compared with the other social groupings. This effect was most obvious in the barren environment. If a behaviour was observed frequently in one member of a family group it normally occurred in the other members of that family. It was twice as likely if the mother of the family initiated a movement that it would be followed by one of her descendants and particularly the younger one. The level of fighting was no different between members of the same family as between members of different families. The evidence for the family group being a socially more complex unit than the other three groups is discussed. The possibility is raised that a socially complex group may be less affected by environmental heterogeneity than groups that were not as well integrated socially.

Temporal Contiguity Between Food Ingestion and Toxicosis Affects the Acquisition of Food Aversions in Sheep

Abstract How quickly toxins can cause ruminants to acquire food aversions has not been studied. Thus, our objectives were to determine the relationship between the time when the toxin lithium chloride (LiCl) was given and when food aversions were acquired by sheep, and to assess when peak levels of Li in the rumen occurred following different methods of administrating LiCl (dissolved in an aqueous solution vs a dry salt in a dissovable gelatin capsule). In Experiment 1, when sheep were gavaged with LiCl (150 mg kg−1 body-weight (BW) in 100 ml water) at either 2, 1 or 0 h prior to ingesting oat chaff, only sheep that received LiCl at time 0 h acquired an aversion to oat chaff, which indicates that the aversion-inducing effects of LiCl occurred within 1 h of its administration. To further assess the relationship between food ingestion, the onset of toxicosis and the acquisition of food aversions, two additional experiments were conducted. In Experiment 2, when sheep ate two familiar foods, alfalfa-grain pellets from 08 : 00 to 08 : 20 h and oat chaff from 08 : 30 to 10 : 30 h, and LiCl was ingested with the pellets, sheep acquired an aversion to the pellets, apparently because the aversion-inducing effects of LiCl occurred shortly after the sheep ate the pellets. Li concentrations in the rumen peaked within 15 min when a solution of LiCl was put directly into the rumen. Conversely, in Experiment 3, when sheep ate alfalfa-grain pellets from 08 : 00 to 08 : 20 h, then received a slowly dissolvable gelatin capsule containing LiCl and then ate oat chaff from 08 : 30 to 10 : 30 h, they acquired an aversion to oat chaff, evidently because the aversion-inducing effects of LiCl occurred coincident with eating the oat chaff. Li concentrations in the rumen peaked after just 1 h when LiCl was given in a gelatin capsule. In summary, sheep experienced the effects of Li within 1 h after it was dispersed in the rumen, which occurred at different times depending on whether LiCl was mixed with the food or administered in capsules, and the acquisition of an aversion to one of two familiar foods depended on the contiguity between food ingestion and when LiCl had its effects.